The chief function of the Neuropathology Core (NC) is to provide state of the art diagnostic services, to set up and maintain a collection of optimally prepared brain samples, and to supply samples for cutting edge research to investigators of the Center, affiliated Centers, and to outside neuroscientists conducting research into neurodegenerative diseases. Because humans are the only known species to naturally develop Alzheimer disease (AD) or related illnesses, the availability of carefully prepared postmortem samples is essential despite the existence of valuable transgenic animal models. Thus, human tissue-dependent studies require that the diagnostic categorization of samples of interest is as accurate as possible. This tissue must be made available quickly following the receipt of a request to enhance laboratory efficiency and productivities. Therefore, the specific aims of NC are: 1. To establish an accurate diagnosis on all brains obtained for the Center including clinico-pathological interpretations of the findings, which are recorded within two standardized reports; a) a text-based for clinicians and medical files, and b) a quantification-based report. The quantification-based report provides data to the Clinical Care / Data Management, and to the National Alzheimer's Coordinating Committee (NACC) in compliance with National Institute on Aging (NIA) requirements. Furthermore, it is used for identifying the samples in storage with variables matching those specified by requestors; 2. To obtain brain samples for tissue-dependent fresh frozen studies with or without requirement of cellular morphology preservation, which are ready for immediate disbursement once categorized; and formalin fixed samples; 3. To organize the collection of samples, maintain it safely, and select among the samples in storage the ones that best match the requirement of a specific study with subsequent distribution within five working days from the time the receipt of the request; 4. To teach clinicians, trainees, and neuroscientists the neuropathology of the dementias, and to assist in correlating findings made in transgenic animal models with those usually occurring in the human brains; and 5. To cooperate with other Centers including the National Institute of Neurological Disorders and Stroke (NINDS) supported Udall Center.